radio, :anmunicatibrz. industrial applications electron g ar d manufacture -., . ' AL .&' The merits of graphite and its desirability as an anode material were recognized by Amperex more than a decade ago. Through the years ... despite the insistence and claims of other tube manufacturers in regard to the superiority of various rare and semi-precious metals ... Amperex has consistently held to its conviction that graphite was the preferred material for anodes in high vacuum tubes. We have demonstrated, during that period, the superiority of our anodes by developing almost 100 types of transmitting tubes that have found favor in commercial broadcasting, aviation and electro -medical fields, as well as tubes for applications in the high and hyper -high frequency range for the armed services of the United States and the United Nations. With our country in dire need of the rare and semi-precious metals employed as anodes by other manufacturers . and with the demand for "military purpose" tubes climbing to staggering quantities ... Amperex is proud of the fact that its perseverence in developing graphite as an anode substance releases strategically necessary metals for other and equally important War efforts. AMPEREX ELECTRONIC PRODUCTS 79 WASHINGTON STREET BROOKLYN, NEW YORK electron ics Vol. 15 A M<GRAW-HILL PUBIIICATION CONTENTS -AUGUST, 1942 WAR TUBES, by Henry Gregg Cover New RCA special purpose tubes BROADCASTING UNDER WAR CONDITIONS, by J. B. Epperson and B. Dudley 34 Technical operation of broadcasting stations adversely affected by shortages KEITH HENNEY of equipment (mostly tubes) and well trained technical personnel. Pooling urged in DCB "share the spare parts" program Editor arrangements of spare parts L. 36 Donald G. Fink Beverly Dudley ELECTRONIC WELDING CONTROL, by H. Palmer Managing Editor Acting First of a series of four articles on present-day practice in controlling ¡weld- problems indplved (on leave) Managing Editor ing operations by means of electron tubes. Gives general in designing controls for resistance welding machines W. W. MacDonald Craig Walsh Associate Editor Associate Editor UNSYMMETRICAL ATTENUATOR NETWORKS, by P. M. Honnell. 41 A method is given for calculating elements of T and tr resistance attenuators M. L. Mattey J. M. Heron between different input and output impedances Assistant Editor Assistant Editor ELECTRONIC SWITCHING IN POWER LINE CARRIER CIRCUITS, Harry Phillips 44 Art Director by J. D. Booth Requirements for electronic switching to provide automatic transmission in both directions in power line carrier systems. Fundamentals are outlined in block diagram form, and an application of this system is given PERIODIC WAVE FORM ANALYSIS, Part II, by H. M. Lewis 48 The concluding part of this article discusses the production of timing axes and wave form control for cathode-ray oscilloscopes by means of amplitude H. W. MATEER and impedance methods of changing wave form of deflecting voltages Publisher BAND PASS AND ELIMINATION FILTERS, by H. Holubow 54 Wallace B. Blood Graphical solution for constant K filters having dissipative elements simplifies Sales Manager design of band pass and band elimination filters J. E. Blackburn, Jr. AND CHARACTERISTIC Circulation PROPAGATION CONSTANT Director of HIGH LOSS LINES, by K. Spangenberg 57 Electronics IMPEDANCE OF This Reference Sheet provides a simple and graphical method for determin- ing the important factors of transmission lines which, being constructed of materials of high resistivity, have high series resistance OCD CARRIER CURRENT TESTS 59 OCD investigates feasibility of using power lines for distributing 720 kc sig- nals in downtown, urban, and suburban areas for wartime communication Contents Copyright, 1942, by Inc. McGraw-Hill Publishing Company, IRE CONVENTION 62 McGRAW-HILL Highlights of the Summer Convention of the Institute of Radio Engineers PUBLISHING COMPANY, INC. JAMES H..McGRAW Founder and Honorary Chairman DEPARTMENTS Publication Office CROSSTALK 33 NEW PRODUCTS 108 119 99-129 North Broadway, Albany, N. Y. ELECTRON ART 62 PATENTS U. S. A. TUBES AT WORK 92 BACKTALK 124 EDITORIAL AND EXECUTIVE OFFICES NEWS OF THE INDUSTRY 101 INDEX TO ADVERTISERS 132 330 West 42nd St., New York, N. Y., U. S. A. James H. McGraw, Jr., President Vice President least ten Howard Ehrlich, Executive August. 1942, Vol. 15: No. 8. Published monthly, price 50c a copy. Allow at ELECTRONICS, to the Director of Mason Britton, Vice Chairman days tor change of address. All communications about subscriptions should be addressed Circulation. 330 West 42nd Street, New York, N. Y. B. Putnam, Treasurer R. Mexico, Central and South American cou ntries, $5.00 a year, Subscription rates-United States and possessions, for two Yeats, Joseph A. Gerardi, Secretary two years, $10.00 for three years. Canada (Canadian funds accepted). $5.50 a year, $9.00 $8.00 for one 72 shillings for three $11.00 for three years. Great Britain and British possessions 36 shillings for year, for three years. Entered as Second Class matter, August 29, Cable Address: years. All other countries. $6.00 for one year. $12.00 Michigan Albany, New York, under the Act of March 3, 1879. BRANCH OFFICES: 520 North 1936, at Post Office, London, W. C. 2; Washington; MCGRAWHILL, New York Avenue, Chicago: 68 Post Street, San Francisco: Aldwvch House, Aldwych, Louis: Boston: Atlanta. Ga. Member A. B. P. Member A. B. C. Philadelphia: Cleveland; Detroit: St. UTC has always been a leader in transformer engineering. In pre-war years, UTC earned an enviable reputation for making possible the job that "couldn't be done". It was only logical, therefore, that when special war requirements came up, UTC was one of the first looked to for the solution of new problems. The research and development in both engineering and production methods for these new designs are naturally cumulative. They are yours for the asking on your present war problems, and assure a continuance of UTC's reputation as "leaders of the field" when victory is ultimately gained. UNITED'TRANSFORMER,soV<aIC.STREET CO NEW 'ORK, N Y. CABLES; "ARLAB PHOENIX is an improved tracing cloth that defies perspiration stains and water marks-that holds pencil smudges and erasure scars at a minimum. Now you can - have clean tracings, in pencil or ink, free from the untidy "ghosts" that reproduce on blueprints! For PHOENIX is ghost -proofed by a remarkable new process that defies moisture, and gives you an unusually durable working surface. You can use harder pencils with this improved cloth and get sharper lines with less tendency to smudge. Even 6H pencil lines show clearly, and reproduce sharply! Erasing does not mar the drawing surface; erased areas take pencil smoothly This New Tracing Cloth -and ink without feathering. The new white color and increased transparency provide excellent drawing contrast uce strong Prevents Scars and Stains Let PHOENIX p ove its merits onyour own drawing board. See your K&E dealer, or write for a generous Drawings working sample and an illustrated brochure. on your EST. 1567 KEUFFEL & ESSER CO. NEW YORK HOBOKEN, N. J. DETROIT MONTREAL CHICAGO ST. LOUIS SAN FRANCISCO LOS ANGELES tt A I / trtR.1 REDUCES PHOENIX DEFIES PHOENIX LESSENS PHOENIX MOISTURE GHOSTS SMUDGE GHOSTS ERASURE GHOSTS improved surface of (be- REG. V.S. PAT. O.F. Perspiration and water splashes The new Ordinary tracing cloths on ordinary tracing cloth create PHOENIX Tracing Cloth per- come scarred when erased... "ghosts" which reproduce on mits you to use harder pencils erased spots produce ghosts blueprints. PHOENIX Tracing (511 and 6H) and to get on blueprints. TRACING CLOTH Cloth withstands actual immer- sharper lines with less ten- min- dency to smudge. PHOENIX has a durable sion in water for fully 10 reduces for pencil and ink utes at a time! Perspiration and Result: Cleaner tracings and drawing surface that water marks will not stain it! blueprints. working scars to a minimum. TYPE 840 High Capacity Available in any temperature coefficient from zero to -.00075 mmf/mmf/C°. (1) Zero Temperature Coefficient up to 1500 MMF. (2) Negative Temperature Coefficient up to 3000 MMF. SIZE: .780" diameter Steatite tube - length varies TYPE 850 High Frequency, High Voltage Unit with capacity and temperature coefficient. 500 MMF NTC approximately 3/4" long. Capacity ranges 1OMMF to 100MMF and 1000 MMF NTC approximately 1" long. intermediate values. Available either Zero 500 MMF ZTC approximately 3/4" long. or Max. Negative temperature coefficient. 1000 MMF ZTC approximately 11/2" long. Standard tolerances as to coefficients and Power factor of .05% - does not increase with ageing. capacity. Size 3/4" long. .765" diameter, exclusive of terminals. Voltage rating - 1000 volts D.C. Leakage more Power Factor .05% does not increase with than 10,000 megohms. ageing. Voltage rating 5000 volts D.C. Terminals - two types available: A.C. voltage rating varies with frequency. (1) Lug .030" thick threaded for 6-32 ma- chine screw, or conventional soldering Terminals available in two types; same as (2) Axial mounting Type 840. post with 6-32 ma- chine screw thread. CENTRALAB: Div. of Globe -Union Inc., Milwaukee, Wis., U. S. A. 4 August 1942 - ELECTRONICS i,. /i . lt`y(i L l Of necessity, tube shown is not a new i development, \VIIr has changed the entire structure of American manufactur- ing with resultant shifting in engineering point of view. Electronic designers are conquering problems never before presented. Many defense developments will-when presented to the post-war commercial market - make unheard of changes in electronic scope. "Secret weapon" is a hackneyed phrase, but would be justified when applied to any number of new applications of electronics. "RADAR," the u. h. f. aviation locator, may, for instance, be staridard equipment on commercial aircraft after the war. Yet it is only one phase of the new developments. The Raytheon laboratories are well in the vanguard of those develop- ing new devices and usages.